This lesson plan can be adapted for students in grades 3-12. Students work in small groups to create two simulations of salmon spawning environments: one healthy, the other unhealthy.
In this activity, students will observe how salmon eggs settle into gravel (the marbles). This simulates what happens to eggs as they are released by the female. She then covers the nest with more gravel, which provides plenty of pockets where salmon eggs can rest protected and still receive enough water. Water cools the eggs and also delivers dissolved oxygen, which the eggs absorb. If eggs are coated with silt or other substances, they can no longer absorb oxygen and will suffocate.
Students will also observe what happens when "silt" (the sand) is added to the water. Silt enters streams through erosion, which can occur naturally as a stream shifts. Human activities, though, cause the most erosion. Once the erosion-causing activity is stopped, streams may cleanse themselves. (Depending on the extent of the problem, self-cleansing can take from one to fifty years.)
- two clear pint containers (such as canning jars)
- one cup of sand
- 24 salmon eggs (from a fish-bait store; these eggs aren't viable)
The student will be able to:
- Identify the environment needed to support good-quality spawning grounds for salmon.
- Identify land-use practices or events that prevent salmon eggs from incubating and hatching.
- Describe their reactions to the experiment in a journal or essay.
- Each group fills the two empty jars half full with marbles.
- Pour enough water into each jar to cover the marbles, but do not fill the jar. (Leave two inches of empty space.)
- Place one dozen salmon eggs in each jar. Observe and discuss what happens.
- Swirl the eggs around slightly. Observe and discuss what happens. (This simulates water flowing over the eggs, keeping them cool and bringing them oxygen.)
- Discuss what might happen if silt suddenly dumps into a stream.
- Now have each group pour one cup of sand into one jar to simulate silt in the stream. Shake the jar gently twice and let the sand settle.
- Allow each group time to discuss its observations and what siltation might mean to salmon eggs.
- Ask each group to discuss its conclusions; list conclusions where all students can see them.
- Engage the entire class in a discussion of the results and what kind of conditions were simulated.
- To increase the challenge and learning opportunity of this activity, you may wish to have the students design their own experiments. Begin the activity by discussing the conditions that salmon eggs require for incubation, and how those conditions might change. Then allow each group of students to decide how to test these conditions. If necessary, specify a length of time for the experiments and set a time for reporting about their methods and results.
- Ask students to investigate the methods and results of various stream clean-up and restoration programs.
- Have students find out if salmon spawning still occurs in Idaho, and where. Investigate the possibility of making a field trip to the site during spawning time. Alternatively, find out if anyone has taped the event and will share the video with the students.
- Encourage students to find community members who can speak to the class about the importance of salmon to local cultures and the economy; or about the management efforts to restore salmon habitat and populations.